The present invention relates to a torque motor with a hydraulic potentiometer for a servo-distributor, intended in particular for the control of jacks and hydraulic motors.
This type of torque motor is intended to control a hydraulic potentiometer composed of four nozzles mounted in a bridge. The output of the torque motor, which is called a blade, causes the cross-section of two nozzles to vary, which generates a pressure differential proportional to the control current of the torque motor.
The torque motor comprises magnets fixed to fixed members in which there is arranged an armature whose ends are separated from the fixed members by an air-gap, and around which armature there are mounted two induction coils which are capable of being supplied with electrical current. The blade is fixed by one of its ends to a flexion tube which is connected to the armature by its corresponding end.
The symmetry of the magnetic circuit assures that no torque acts on the armature in the absence of current in the coils. On the other hand, when these coils are supplied with current in the suitable direction so as to cause their magnetic fields to be added, each end of the armature is polarized and is subjected, in the air-gaps, to an electromagnetic force which creates a torque causing bending of the tube, which in turn moves the blade between the two associated nozzles.
Certain torque motors are provided with a single magnet and others with two. These magnets are generally U-shaped and have housing machined therein for fixing screws to the fixed members. The result is that those magnets have a relatively complicated geometry which causes manufacturing difficulties. In addition, they occupy considerable space and have a low coercive field, such that if the motor is disassembled, they must subsequently be remagnetized before reassembly.